1. Field of the Invention
The invention relates to a spray pump of the type comprising: a main cylinder in which there is defined a pumping chamber; a main piston mounted to slide in said main cylinder between a first inactive position and a second end-of-stroke position, said piston being extended by a hollow rod and having a valve seat therein; first spring means urging said piston to said first position; a secondary cylinder comprised within the main cylinder; a secondary piston mounted to slide within said secondary cylinder between a first closed position and a second open position, said piston being provided with an upper extension having an end applicable against said valve seat; and second spring means urging said secondary piston to said first position thereof.
2. Description of the Prior Art
Frequently in ordinary daily life, it is necessary to spray liquids of quite diverse viscosities towards certain surfaces or spaces. This need is observed, for example, during personal toilet operations to spray lotions, scented waters, deodorants or other products on the human body; and also for domestic cleaning, as also for spraying insecticides, air fresheners, etc.
On such occasions, a strong spray is required, without the intensity thereof being weak at the start or end of the spraying operation since, in this case, the spray is preceded and/or followed by a weak jet which does not attain the desired objective and, therefore, is wasted or even may produce undesired effects, such as stains, drips, etc.
Pumps producing a precompression of the product to be dispensed are already know and the result of said precompression is to allow the vigorous spray mentioned above.
Some of the known pumps are provided with a single spring or resilient means fulfilling two missions, i.e. of causing the piston to recover the starting position thereof after the pump has been operated and of providing the desired precompression; these pumps, therefore, have the drawback of not allowing the recovery speed or conditions and the degree of precompression to be adjusted separately.
The operation of another type of known pumps, as indicated at the beginning, is based on a predetermined ratio between the force of the two spring means provided, such that one of the springs may not be altered unilaterally, without substantially altering the operation of the pump or even preventing it from working.
Since is not possible to change the corresponding resilient means or springs freely or independently in the known, pumps, their field of application becomes, therefore, limited, obliging the manufacture of different pumps for different applications, thereby preventing the manufacture of long runs with the logical effect on costs.
Finally, a third group of pumps having independently replaceable springs may be cited. Nevertheless, these other known pumps suffer various drawbacks, such as a premature, albeit limited communication of the pumping chamber with the outside.